Polycarbonate of alkyl cyclohexylidene bisphenol

ABSTRACT

Thermoplastic aromatic polycarbonates having average molecular weights Mw of at least 10,000 which contain bifunctional carbonate structural units corresponding to formula (I) ##STR1## in which R 1 , R 2 , R 3  and R 4  independently of one another represent hydrogen, a C 1  -C 12  hydrocarbon radical, halogen and 
     R 5 , R 6  and R 7  represent hydrogen, iso-C 3  -C 5  -alkyl, 
     one of the substituents R 5 , R 6  or R 7  not being hydrogen, in quantities of from 100 to 1 mol-%, based on the total quantity of difunctional carbonate structural units in the polycarbonate.

This invention relates to thermoplastic aromatic polycarbonates havingaverage molecular weights Mw of at least 10,000, preferably in the rangefrom 10,000 to 250,000 especially 10,000 to 120,000 and, morepreferably, in the range from 15,000 to 80,000 especially 20,000 to60,000, which contain bifunctional carbonate structural unitscorresponding to formula (I) ##STR2## in which R¹, R², R³ and R⁴independently of one another represent hydrogen, a C₁ -C₁₂ hydrocarbonradical, halogen and

R⁵, R⁶ and R⁷ represent hydrogen, iso-C₃ -C₅ -alkyl, one of thesubstituents R⁵, R⁶ or R⁷ not being hydrogen, in quantities of from 100to 1 mol-%, preferably in quantities of from 100 to 5 mol-% and, morepreferably, in quantities of from 100 to 20 mol-%, based on the totalquantity of difunctional carbonate structural units in thepolycarbonate.

Japanese Patent Nos. 61 062 039, 61 062 040 and 61 105 550 describepolycarbonates consisting completely or partly of structural unitscorresponding to formula (IA) ##STR3## in which R¹ and R² are hydrogen,halogen or methyl and

R is hydrogen, halogen, OH, COOH, acetyl or C₁ -C₄ alkyl (C₁ -C₅ alkylin JP 61 062 040).

Polycarbonates consisting completely or partly of units corresponding toformula (IA), in which R¹, R² and R are hydrogen, are used in theExamples of these patent specifications. These patent specifications donot contain any hint indicating that corresponding polycarbonates, inwhich R is C₁ -C₅ alkyl instead of hydrogen, might have betterproperties. Instead, there is reason to believe that the unsubstitutedcyclohexylidene ring in the polycarbonate structural unit (IA) wasregarded as the best mode in these patent specifications as only suchpolycarbonates are contained in the working Examples.

It has now been found that the polycarbonates according to the inventionhave suprisingly high glass transition temperatures Ta, even whencontaining only such amounts of structural units of formula (I). Theyalso have an especially advantageous mould release behavior,expceptional melt flow taking into account their high glass transitiontemperature Tg. They are additionally tracking resistant, stable tohydrolysis and ageing resistant.

The carbonate structural units corresponding to formula (I) are based onbisphenols corresponding to formula (II) ##STR4## in which R¹, R², R³,R⁴, R⁵ and R⁷ have the same meaning as in formula (I).

In formulae (I) and (II), R¹, R², R³ and R⁴ are preferably hydrogen,methyl, ethyl, phenyl, cyclohexyl, chlorine and bromine and, morepreferably, hydrogen, methyl and bromine.

If more than one of the substituents R¹, R², R³ and R⁴ is not hydrogen,identical substituents are preferred. If two of the substituents R¹, R²,R³ and R⁴ are not hydrogen, o,o'-substitution, with reference to thecarbonate groups (formula (I)) or to the phenolic OH groups (formula(II)), is preferred. If none of the four substituents R¹, R², R³ and R⁴is hydrogen, the o,o,o',o'-substitution, (reference as before), ispreferred.

In formulae (I) and (II), R⁵, R⁶ and R⁷ are hydrogen and iso-C₃ -C₅-alkyl such as isopropyl, tert.-butyl, 1-methylpropyl,1,1-dimethylpropyl, 1-methylbutyl, 1,2-dimethylpropyl and2,2-dimethylpropyl, preferably isopropyl, tert.-butyl, 1-methylpropyland 1,1-dimethylpropyl; more preferably tert.-butyl and1,1-dimethylpropyl and, most preferably, tert.-butyl.

Any iso-C₃ -C₅ -alkyl substituent in formulae (I) and (II) is preferablyin the 4-position in the cyclohexylidene ring (R₅ and R₇ =H; R₆ =iso-C₃-C₅ -alkyl), when availability of the starting material is of primaryconcern and in the 3-position when exceptional heat stability of thepolycarbonate is required.

The following are examples of bisphenols corresponding to formula (II):

1,1-bis-(4-hydroxyphenyl)-4-isopropyl-cyclohexane

1,1-bis-(4-hydroxyphenyl)-4-tert.-butyl-cyclohexane

1,1-bis-(4-hydroxyphenyl)-4-(1-methylpropyl)-cyclohexane

1,1-bis-(4-hydroxyphenyl)-4-(1,1-dimethylpropyl)-cyclohexane

1,1-bis-(4-hydroxyphenyl)-3-isopropyl-cyclohexane

1,1-bis-(4-hydroxyphenyl)-3-tert.-butyl-cyclohexane

1,1-bis-(4-hydroxyphenyl)-3-(1-methylpropyl)-cyclohexane

1,1-bis-(4-hydroxyphenyl)-3-(1,1-dimethylpropan)-cyclohexane

1,1-bis-(3-methyl-4-hydroxyphenyl)-4-tert.-butyl-cyclohexane

1,1-bis-(3-methyl-4-hydroxyphenyl)-4-(1,1-dimethylpropyl)-cyclohexane

1,1-bis-(3-chlor-4-hydroxyphenyl)-4-tert.-butyl-cyclohexane

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-4-tert.-butyl-cyclohexane

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-4-(1,1-dimethylpropyl)-cyclohexane

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-3-isopropyl-cyclohexane

1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-3-tert.-butyl-cyclohexane

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-tert.-butyl-cyclohexane

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-(1,1-dimethylpropyl)-cyclohexane

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-isopropyl-cyclohexane

1,1-bis-(3,5-dichlor-4-hydroxyphenyl)-4-(1-methyl-propyl)-cyclohexane

Bisphenols corresponding to formula (II) are known or may be obtained byknown methods from corresponding ketones and phenols.

In addition to the carbonate structural units corresponding to formula(I), the polycarbonates according to the invention containquantities--complementary to 100 mol-%--of other difunctional carbonatestructural units, for example those corresponding to formula (III) belowwhich are based on bisphenols corresponding to formula (IV): ##STR5##

Bisphenols corresponding to formula (IV) are those in which Z is a C₆₋₃₀aromatic radical which may contain one or more aromatic nuclei, may besubstituted and may contain aliphatic radicals or other cycloaliphaticradicals than those corresponding to formula (II) or heteroatoms asbridge members.

Examples of diphenols corresponding to formula (IV) are hydroquinone,resorcinol, dihyroxydiphenyls, bis-(hydroxyphenyl)-alkanes,bis-(hydroxyphenyl)-cycloalkanes, bis-(hydroxyphenyl)-sulfides,bis-(hydroxyphenyl)-ethers, bis-(hydroxyphenyl)-ketones,bis-(hydroxyphenyl)-sulfones, bis-(hydroxyphenyl)sulfoxides,α,α'-bis-(hydroxyphenyl)-diisopropylbenzenes and nucleus-alkylated andnucleus-halogenated compounds thereof.

These and other suitable diphenols are described, for example, in U.S.Pat. Nos. 3,028,365, 2,999,835, 3,148,172, 3,275,601, 2,991,273,3,271,367, 3,062,781, 2,970,131 and 2,999,846; in DE-OSS 1 570 703, 2063 050, 2 063 052, 2 211 956; in FR-PS 1 561 518 and the book by H.Schnell entitled "Chemistry and Physics of Polycarbonates", IntersciencePublishers, New York 1964.

Preferred other diphenols are, for example, 4,4'-dihydroxydiphenyl,2,2-bis-(4-hydroxyphenyl)-propane,2,4-bis-(4-hydroxyphenyl)-2-methylbutane,1,1-bis-(4-hydroxyphenyl)-cyclohexane,α,α'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene,2,2-bis-(3-methyl-4-hydroxyphenyl)-propane,2,2-bis-(3-chloro-4-hydroxyphenyl)-propane,bis-(3,5-dimethyl-4-hydroxyphenyl)-methane,2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,bis-(3,5-dimethyl-4-hydroxyphenyl)sulfone,2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane,1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane,α,α'-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene,2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.

Particularly preferred diphenols corresponding to formula (IV) are, forexample, 2,2-bis-(4-hydroxyphenyl)-propane,2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane,2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane and1,1-bis-(4-hydroxyphenyl)-cyclohexane.

2,2-Bis-(4-hydroxyphenyl)-propane is particularly preferred.

The other diphenols may be used both individually and also in admixture.

Small quantities (from 0.05 to 2.0 mol-%, based on diphenols used) oftrifunctional or more than trifunctional compounds, particularly thosecontaining three or more than three phenolic hydroxyl groups, mayoptionally be used in known manner as branching agents to obtainbranched polycarbonates. Some of the compounds containing three or morethan three phenolic hydroxyl groups which may be used for branching arephloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hept-2-ene,4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane,1,3,5-tri-(4-hydroxyphenyl)-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane,tri-(4-hydroxyphenyl)phenylmethane,2,2-bis-(4,4-bis-(4-hydroxyphenyl)-cyclohexyl)-propane,2,4-bis-(4-hydroxyphenylisopropyl)-phenol,2,6-bis-(2-hydroxy-5'-methylbenzyl)-4-methylphenol,2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane,hexa-(4-(4-hydroxyphenylisopropyl)-phenyl)-o-terephthalicacid ester,tetra-(4-hydroxyphenyl)-methane,tetra-(4-(4-hydroxyphenylisopropyl)-phenoxy)-methaneand 1,4-bis-((4',4"-dihydroxytriphenyl)-methyl)-benzene.

Some of the other trifunctional compounds are 2,4-dihydroxybenzoic acid,trimesic acid, cyanuric chloride and3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

Monofunctional compounds are used in known manner in typicalconcentrations as chain terminators for regulating molecular weight.Suitable compounds are, for example, secondary amines, phenols and acidchlorides. It is preferred to use phenols, for exampletert.-butylphenols, or other alkyl-substituted phenols. Small quantitiesof phenols corresponding to formula (V) ##STR6## in which R is abranched C₈ and/or C₉ alkyl radical, are particularly suitable forregulating molecular weight. The percentage of CH₃ protons in the alkylradical R is preferably from 47 to 89% and the percentage of CH and CH₂protons from 53 to 11%. In addition, R is preferably in the o- and/orp-position to the OH group and the upper limit to the ortho componentis, more preferably, 20%.

Some particularly suitable phenols are phenol, p-tert.-butylphenol,hydroxydiphenyl, p-cumylphenol and, in particular,p-3,5-dimethylheptylphenol and m- and p-1,1,3,3-tetramethylbutylphenol.The chain terminators are generally used in quantities of from 0.1 to 10mol-% and preferably in quantities of from 0.5 to 8 mol-%, based ondiphenols used.

The polycarbonates according to the invention may advantageously beproduced in known manner by the phase interface polycondensation process(cf. H. Schnell, "Chemistry and Physics of Polycarbonates", PolymerReviews, Vol. IX, pages 33 et seq., Interscience Publishers, 1964).

In this process, the diphenols corresponding to formula (II) aredissolved in aqueous alkaline phase. To prepare copolycarbonates withother diphenols, mixtures of diphenols corresponding to formula (II) andthe other diphenols, for example those corresponding to formula (IV),are used. Chain terminators, for example corresponding to formula (V),may be added to regulate molecular weight. The reaction with phosgene isthen carried out by the interfacial condensation method in the presenceof an inert organic phase which preferably dissolves polycarbonate. Thereaction temperature is generally in the range from 0° C. to 40° C.

The 0.05 to 2 mol-% of branching agents to be optionally used may eitherbe initially introduced with the diphenols in the aqueous alkaline phaseor may be added in solution in the organic solvent before thephosgenation.

In addition to the diphenols of formula (II) to be used and the otherdiphenols corresponding to formula (IV), it is also possible to usemono-and/or bis-chlorocarbonic acid esters thereof, which are added insolution in organic solvents. The quantity of chain terminators and ofbranching agents is then determined by the mols of diphenolatestructural units corresponding to formula (II) and, optionally, of theother diphenolate structural units, such as for example thosecorresponding to formula (IV). Similarly, where chlorocarbonic acidesters are used, the quantity of phosgene may be reduced accordingly inknown manner.

Chlorinated hydrocarbons for example, such as chloroform,dichloroethane, di-and tetrachloroethylene, tetrachloroethane, methylenechloride, chlorobenzene and dichlorobenzene, and also non-chlorinatedhydrocarbons, such as for example toluene and xylene, and mixtures ofthese solvents, particularly mixtures of methylene chloride andchlorobenzene, may be used as the organic phase for the interfacialpolycondensation and as organic solvent for the solution of the chainterminators and, optionally, for the branching agents and thechlorocarbonic acid esters. The chain terminators and branching agentsused may optionally be dissolved in the same solvent.

The organic phase used for the phase interface polycondensation may be,for example, methylene chloride, chlorobenzene or toluene and alsomixtures of methylene chloride and chlorobenzene.

Aqueous NaOH solution or KOH solution for example is used as the aqueousalkaline phase.

The production of the polycarbonates according to the invention by thephase interface polycondensation process may be catalyzed in knownmanner by such catalysts as tertiary amines and phase transfercatalysts, particularly tertiary aliphatic amines such as, for example,tributylamine, triethylamine, N-ethyl piperidine and, in particular,quaternary ammonium and phosphonium compounds and crown ethers, such asfor example tetrabutyl ammonium bromide and triphenyl benzyl phosphoniumbromide. The catalysts are generally used in quantities of from 0.05 to30 mol-%, based on the mols of diphenols used. The catalysts aregenerally added before the beginning of phosgenation or during or evenafter phosgenation.

The polycarbonates according to the invention are isolated in knownmanner, for example by separating off the organic phase containing thedissolved polycarbonate obtained in the phase interfacepolycondensation, washing until neutral and free from electrolyte andthen isolating the polycarbonate in the form of a granulate, for examplein an evaporation extruder, or in the form of a powder or pellets byprecipitation using a non-solvent and subsequent drying or by sprayevaporation.

The high molecular weight, thermoplastic aromatic polycarbonatesaccording to the invention may also be prepared by the knownhomogeneous-phase process, the so-called "pyridine process", and by theknown melt transesterification process, for example usingdiphenylcarbonate instead of phosgene. In these cases, too, thepolycarbonates according to the invention are isolated in known manner.

The additives normally used for thermoplastic polycarbonates, such asstabilizers, mold release agents, pigments, flameproofing agents,antistatic agents, fillers and reinforcing materials, may be added tothe polycarbonates according to the invention in the usual quantitiesbefore or after their processing.

As flameproofing additives there can be used:

1. Alkali, alkaline earth and ammonium salts of aliphatic and aromaticsulfonic acids, carboxylic acids and phosphonic acids. These can besubstituted in different ways, for instance, by F, Cl, Br, alkyl. Salttype flameproofing agents of this kind can also be oligomeric orpolymeric. Salt type flameproofing additives are inter alia described inthe following patent applications: DE-OS 1 694 640, 1 930 257, 2 049358, 2 212 987, 2 149 311, 2 253 072, 2 703 710, 2 458 527, 2 458 968, 2460 786, 2 460 787, 2 460 788, 2 460 935, 2 460 937, 2 460 944, 2 460945, 2 460 946, 2 461 063, 2 461 077, 2 461 144, 2 461 145, 2 461 146, 2644 114, 2 645 415, 2 646 120, 2 647 271, 2 648 128, 2 648 131, 2 653327, 2 744 015, 2 744 016, 2 744 016, 2 744 017, 2 744 018, 2 745 592, 2948 871, 2 948 439, 3 002 122.

2. Organic halogen compounds optionally combined with synergists, forinstance, halogenated aromatic compounds. Such flameproofing agents aredescribed inter alia in the following patent applications: DE-OS 2 631756, JA 51-119 059, DE-OS 3 342 636, EP-A 31 959, DE-OS 3 010 375, 2 631756.

3. Halogenated phthalimides or phthalimide sulfonates: DE-OS 2 703 710,3 203 905, 3 322 057, 3 337 857, 3 023 818.

4. Salts of halogenated complexed acids such as cryolite, salts oftetrafluoroboric acid and of fluorosalicic acid described inter alia inDE-OS 2 149 311 and 3 023 818.

5. Partly or totally fluorinated polyolefines described, for instance,in DE-OS 2 535 262, 2 915 563, 2 948 439, 3 023 818.

6. Sulfonamides, disulfonamides and salts thereof: EP-A 71 125, 14 322,WO 86/4911.

7. Elementary sulfur or red phosphorous: DE-OS 2 345 508, 2 355 211.

8. Ferrocene or its derivatives: DE-OS 2 644 437.

9. Diphenylsulfone: DE-OS 2 129 204.

10. Nickel salts: DE-OS 1 918 216.

11. Polyphenylenesulfide: DE-OS 2 503 336, EP-A 87 038.

12. Alkali and alkaline earth as well as zinc salts of hydrochloricacid, sulfuric acid, phosphoric acid, nitric acid, hydrogen sulfide,boric acid as well as acetic salts of these acids: WO 87/542, U.S. Pat.No. 4,408,005, EP-A 174 864.

13. Siloxanes: DE-OS 2 535 261.

As comonomers which are useful for flameproofing there are described:

1. Chlorinated and brominated bisphenol A and 4,4'-dihydroxydiphenylsulfide: EP-A 31 958, 61 060.

2. Siloxane blocks: DE-OS 3 334 782.

3. Dihydroxydiphenyl sulfone: U.S. Pat. No. 3,912,688.

4. Sulfo anilide end groups: EP-A 82 483.

Flameproofing methods can be applied individually or combined.

Flameproofing additives are incorporated into the polycarbonates whichcontain diphenols of formula (I) in polymerized form preferably inextruders or kneaders individually or combinated. In many cases theflameproofing additives can be added to the polycarbonates during themanufacture or even to the starting materials. It is also possible toadd flameproofing additives to solutions of the polycarbonates withsubsequent removal of the solvent. The amounts of flameproofingadditives are preferably 0.001 to 50% by weight in case of monomerspreferably 0.1 to 50 mol-%.

More specifically for example graphite, carbon black, metal fibres,metal powder, silica, quartz, talcum, mica, caoline, clays, CaF₂, CaCO₃,aluminum oxide, glass fibres, carbon fibres, ceramic fibres, organic andinorganic pigments can be added and as mould release agent, forinstance, glyceral stearate, pentaerythrite tetrastearate andtrimethylolpropane tristearate.

The polycarbonates according to the invention can be processed accordingto known methods of thermoplastic shaping to yield shaped articles. Thiscan be done, for instance, by extruding the recovered polycarbonates toa granulate and fabricating the granulates optionally after adding theabove-identified agents, for instance, by injection moulding, extrusion,blowing, rotation, casting or hot pressing. Shaped articles manufacturedin this way include fibres, plates and sheets. Sheets can be for theprocessed by deep drawing. Also films can be manufactured and can becombined with other films. The polycarbonates of the invention can alsobe used in combination materials such as combined with fibres and otherpolymers.

Shaped articles of polycarbonates according to the invention can beused, for instance, in electrical appliances or in construction withparticular advantage when complicated parts required dimensionalstability under heat are to be produced.

Moulded articles include fibres, plates and films. Films can also beshaped by deep-drawing. Films can be fabricated into composite films.The polycarbonates can also be used in combination with other materialssuch as fibres and other plastics.

EXAMPLE 1 Polycarbonate of 1,1-bis-(4-hydroxyphenyl)-4-tert.-butyl-cyclohexane

324 g (1 mol) 1,1-bis-(4-hydroxyphenyl)-4-tert. -butyl-cyclohexane weredissolved in 3 l water. 3 l methylene chloride with 6.8 g (0.033 mol)4-(1,1,3,3-tetramethylbutyl)-phenol dissolved therein were added to theresulting solution. 148.5 g (1.5 mol) phosgene were then introduced intothe mixture over a period of 30 minutes with intensive stirring at 25°C. After the addition of 1.13 g (0.01 mol) N-ethyl piperidine, themixture was intensively stirred for 60 minutes at 25° C. Thebisphenolate-free aqueous phase was separated off. After acidificationwith dilute phosphoric acid, the organic phase was washed with wateruntil free from electrolyte and concentrated by evaporation. Thepolycarbonate obtained was then freed from the remaining methylenechloride by drying. It was colorless and showed a relative viscosityη_(rel) of 1.313 (as measured on a methylene chloride solution, c=5 g/l,at 25° C.). The glass temperature Tg (according to differential thermalanalysis) was 221° C.

EXAMPLE 2 Polycarbonate of1,1-bis-(4-hydroxyphenyl)-4-(1,1-dimethylpropyl)-cyclohexane

The procedure was as in Example 1 except that 338 g (1 mol)1,1-bis-(4-hydroxyphenyl)-4-(1,1-dimethylpropyl)-cyclohexane was usedinstead of the bisphenol. The polycarbonate obtained had a relativeviscosity of 1.334 (as measured on a methylene chloride solution, c=5g/l, at 25° C.). The glass temperature Tg (according to differentialthermal analysis) was 201° C.

EXAMPLE 3 Copolymer of bisphenol A and1,1-bis-(4-hydroxyphenyl)-4-tert.-butyl-cyclohexane in a molar ratio of1:1

The procedure was as in Example 1, except that half the bisphenol usedwas replaced by 114 g (0.5 mol) 2,2-bis-(4-hydroxyphenyl)-propane(bisphenol A).

The polycarbonate obtained had a relative viscosity η_(rel) of (asmeasured in a methylene chloride solution at 25°, c=5 g/l. The glasstemperature Tg (according to differential thermal analysis) was 192° C.

EXAMPLE 4 Polycarbonate of1,1-bis-(4-hydroxyphenyl)-3-tert.-butyl-cyclohexane

The procedure was as in Example 1, except that the bisphenol used wasreplaced by 324 g (1 mol) 1,1-bis-(4-hydroxyphenyl)-3-tert.-butyl-cyclohexane. The polycarbonate obtained had a relative viscosityof 1,309 (as measured in a methylene chloride solution, c=5 g/l, at 25°C.). The glass temperature T_(g) (according to differential thermalanalysis) was 239° C.

EXAMPLE 5 Polycarbonate of1,1-bis-(4-hydroxyphenyl)-3-(1,1-dimethylpropyl)-cyclohexane

The procedure was as in Example 1, except that the bisphenol used wasreplaced by 268 g (1 mol)1,1-bis-(4-hydroxyphenyl)-3-(11-dimethylpropyl)-cyclohexane. Thepolycarbonate obtained had a relative viscosity of 1,314 (as measured ina methylene chloride solution, c=5 g/l, at 25° C.). The glasstemperature T_(g) (according to differential thermal analysis) was 220°C.

EXAMPLE 6

Example 1 was repeated but 10 Mol-% of diphenol was replaced by3,3',5,5'-tetrabromo-bisphenol A. The resulting polycarbonate had anη_(rel) of 1.302.

EXAMPLES 7-46

The results of burning tests of polycarbonates equipped with flameproofing agents are summarised in table 1. The flame-proofing agentswere incorporated by means of a twin screw extruder ZSK of Werner andPfleiderer.

Burning behavior was evaluated on the basis of the O₂ -index accordingto ASTM 2863-70. For these tests specimen of 80×6×3 mm were made byinjection moulding.

                                      TABLE 1                                     __________________________________________________________________________              Polycarbonate                                                                           flame proofing                      O.sub.2 -Index,       Example   of example                                                                              agent                         Amount,                                                                             %                     __________________________________________________________________________     7 (Comparison)                                                                         1         --                            --    24,1                   8 (Comparison)                                                                         2         --                            --    24,5                   9 (Comparison)                                                                         3         --                            --    24,3                  10        6         --                            --    28,6                  11        1         K-p-toluenesulfonate          0,2   28,2                  12        2         "                             "     28,8                  13        3         "                             "     28,5                  14        6         "                             "     33,4                  15        1         perfluoro-n-butane-K-sulfonate                                                                              "     29,4                  16        2         CF.sub.3CO.sub.2CaO.sub.2 CCF.sub.3                                                                         "     28,9                  17        1                                                                                        ##STR7##                     "     29,5                  18        1                                                                                        ##STR8##                     "     30,7                  19        3         "                             "     30,5                  20        1         decabromo diphenyl            5     29,0                  21        2         "                             5     30,2                  22        1         decabromo + Sb.sub.2 O.sub. 3 5 + 2 31,8                  23        1                                                                                        ##STR9##                     3     31,0                  24        1         Na.sub.3 AlF.sub.6            0,2   29,7                  25        3         "                             0,2   30,4                  26        3         Na.sub.3 AlF.sub.6 + polytetra-                                                                             0,2 + 0,1                                                                           33,3                                      fluoroethylene as example 27                              27        3         polytetrafluoroethylen,       0,2   26,7                  28        1         Hostaflon 1740, Hoechst AG    0,2   27,2                  29        1                                                                                        ##STR10##                    0,4   29,5                  31        1         red phosphorous average       5     36,1                                      particle diameter 25 μm                                32        1         Ferrocene, average            0,1   27,2                                      particle diameter 28 μm                                33        1         diphenylsulfone               3     27,3                  34        1         Ni-Laurinate                  0,2   27,5                  35        1         Polyphenylenesulfide          10    31,5                                      according to                                                                  EP-A 171 021, melt            10    31,7                  36        3         viscosity 53 Pa.s at a                                                        shear rate of 100 Pa at                                                       306° C.                                            37        1         NaCl                          0,3   27,6                  38        1         K.sub.2 HPO.sub.4             0,2   28,5                  38a       1         Li.sub.2 SO.sub.4             0,2   27,9                  39        1         NaNO.sub.3                    0,2   30,3                  40        1         ZnS                           0,5   28,5                  41        3         ZnS                           0,5   28,6                  42        1         NaHS                          0,2   27,0                  43        1         Na.sub.3 B.sub.4 O.sub.7      0,2   28,2                  44        1         Polydimethylsiloxane          7     28,7                                      of viscosity 170 000 mPa.s                                45        1         Polysiloxane block-co-        50    28,9                                      polycarbonate of example                                                      3 of DE-OS 3 334 782                                      46        2         K-salt of perfluoro-n-butane  0,2 + 0,1                                                                           33,1                                      sulfonic acid + Polytetra-                                                    fluoro-ethylene (example 27)                              __________________________________________________________________________

We claim:
 1. A moulding composition comprising a thermoplastic aromaticpolycarbonate resin having a weight average molecular weight of at least10,000 comprising bifunctional carbonate structural units correspondingto ##STR11## in which R¹, R² R³ and R⁴ independently of one anotherrepresent hydrogen, a C₁ -C₁₂ hydrocarbon radical, halogen andR⁵, R⁶ andR⁷ represent hydrogen, iso-C₃ -C₅ -alkyl, one of the substituents R⁵, R⁶or R⁷ being other than hydrogen, in quantities of from 100 to 1 mol-%,based on the total quantity of difunctional carbonate structural unitsin the polycarbonate
 2. The composition of claim 1 wherein saiddifunctional carbonate structural units comprise units corresponding to##STR12## wherein Z is a C₆₋₃₀ aromatic radical.
 3. The composition ofclaim 1 further comprising at least one member selected from the groupconsisting of a stabilizer, mold release agent, pigment, flameproofagent, antistatic agent, conductivity increasing agent, a filler and areinforcing agent.